Method of making concrete bodies

ABSTRACT

A CONCRETE BODY IS FORMED WITH A PERFORATE TUBE OR TUBES ENCASED IN A FILTER SLEEVE IMMERSED IN THE CONCERETE. THE TUBE MAY BE INSTALLED BY INSERTING IT INTO THE HOLLOW SHAFT OF AN AUGER AND INJECTING GROUT THROUGH THE SHAFT WHILE THE AUGER IS WITHDRAWN THEREBY LEAVING THE TUBE EMBEDDED IN THE GROUT. ALTERNATIVELY, THE TUBE MAY BE INSERTED DIRECTLY INTO FRESHLY PLACED CONCRETE OR MAY BE SET IN AN OPEN HOLE OR CASING OR FORM PRIOR TO PLACEMENT OF THE CONCERETE OR GROUP. WITH EITHER METHOD, THE TUBE FORMS A HOLLOW CORE BY WHICH EXCESS WATER MAY BE REMOVED TO IMPROVED THE QUALITY OF THE CONCRETE. ALSO, THE CORE MAY BE USED FOR INSERTING A VIBRATORY SOURCE, TESTING EQUIPMENT, INSTALLING REINFORCING MEMBERS, OR OTHER USEFUL PURPOSES.

@ct. 12, 19 D. s. DACZKO 3,,ML735 METHOD OF MAKING CONCRETE BODIES Filed Oct. 24, 1968 I FIG. I (PRIOR ART) INVI'JN'IUR. DONALD S. DACZKO 7 ATTORNEYS.

ted States US. Cl. 6]l53.64 16 Claims ABSTRACT OF THE DISCLOSURE A concrete body is formed with a perforate tube or tubes encased in a filter sleeve immersed in the concrete. The tube may be installed by inserting it into the hollow shaft of an auger and injecting grout through the shaft while the auger is withdrawn thereby leaving the tube embedded in the grout. Alternatively, the tube may be inserted directly into freshly placed concrete or may be set in an open hole or casing or form prior to placement of the concrete or grout. With either method, the tube forms a hollow core by which excess water may be removed to improve the quality of the concrete. Also, the core may be used for inserting a vibratory source, testing equipment, installing reinforcing members, or other useful purposes.

This invention broadly relates to the art of forming concrete bodies, more particularly to the art of forming columns in the earths surface and still more particularly, to a hollow core concrete pile construction and method of making same.

The invention is particularly applicable to the forming of concrete piles in the earths surface and will be described with particular reference thereto; however, it is to be appreciated that the principles of this invention have other applications and may be employed wherever it is desired to form concrete bodies and particularly bodies of columnar shape. The invention is particularly useful where columns are to be formed in earth in which there is a substantial quantity of ground water present whether artesian or otherwise, or where it is desirable for convenience in concrete placement that excess water is required to render the mix workable.

It has become conventional practice in the installation of concrete piling to form a hole in the earth to the desired depth by augering or excavating a hole in the earth or by driving into the earth a hollow tubular mandrel closed at its lower end. Where augering or excavating procedures are used and where the soil is self supporting, concrete is simply poured into the excavation to form a subsurface structural column, referred to variously as a pile or caisson. Where the soil is not self supporting, the thin wall metal casing may be inserted into the excavation as it is being formed. The casing may or may not be withdrawn concurrently with the placement of concrete. In those cases where a tubular steel mandrel is driven into the earth, the lower end may be so arranged that it may be opened or removed as concrete is placed into the hollow steel mandrel, the mandrel then being withdrawn as concrete is being placed. Occasionally, it may be desirable to leave the bottom closure in place and to fill the steel mandrel or shell with concrete.

In all instances described above, a generally elongated column of fluid concrete is placed. However, gravitational effects on the solid particles of the concrete tend to cause segregation in the fluid column, the large particles of coarse aggregate tending to settle to the bottom, the lighter particles such ase portland cement together with the mixing water tending to rise toward the top.

The presence of water channeling upward is characterized externally by a noticeable bubbling or disturbance at 3,6lllfl35 Patented Oct. 12, 1971 the upper surface of the concrete column and the subsequent collection of this water above the concrete or grout surface. In the interior of the column, the finer grains of cementitious materials are being carried to the surface by the escaping water, leaving behind the coarser particles of sand, stone, or other aggregate. The result of this segregation process is that the homogeneous nature of the concrete is altered in the areas of the channeling and sand pockets or columns containing little or no cementitious materials are formed at random points throughout the column.

By reason of the fact that the concrete must be caused to flow readily down an opening of relatively small diameter for an appreciable distance, often around steel members which have been placed in the opening, it is essential that the concrete mix be highly fluidant to reduce, in as far as possible, the tendency toward formation of voids within the concrete. Such highly fluidant mixes are far more susceptible to segregation than are the concrete mixes which are normall placed in relatively shallow areas of relatively large cross sections, such as floor slabs.

Furthermore, whenever concrete placed in the manner described above comes in contact directly with surrounding soil, there is a tendency for ground water commonly present in such soil to flow inwardly to the fluid column of concrete, further increasing the water content of the concrete and thereby further increasing the tendency towards segregation.

It is standard practice in concrete technology to use as low a water content in concrete as practicable, not only to avoid the adverse effects of segregation described above but also because the strength of finished concrete is principally a function of the water/cement ratio, the strength varying inversely with this ratio.

Thus, grout having a water-cement ratio below about 0.35 is almost non lowable or is a rigid mass having little if any strength but which hardens to an ultimate strength much greater than the grouts of the higher water-cement ratios. Maximum strength for most portland cements is obtained when the water-cement ratio is about 0.25. However, to facilitate the injection of the grout, it is desirable that the grout have a water-cement ratio of 0.45 or higher. Thus, it is highly desirable that the grout have a high water-cement ratio during the injection process but have a low water-cement ratio when it is in position and hardening. Obviously, it is not sufiicient to rel on the dissipation of the water into the surrounding soil as the means for reducing the water-cement ratio of the injected grout nor is it satisfactory to permit the water to channel upward through random flows paths in the column due to the danger of forming sand pockets or columns contammg little or no cementitious material as described above.

The present invention contemplates an improved concrete body and method of constructing the same WhlCh overcomes all of the above referred to problems, and others, and which is simple and economical and which results in the formation of a concrete body having improved structural characteristics. i

In accordance with a broad aspect of th1s 1nvent1on, there is provided an improved method of forming a concrete body.

More specifically, and'in accordance with the present invention, an improved concrete body and method of making same is provided wherein the concrete body is cast in place with a hollow core which provides a controlled flow path for the release of water while the concrete is setting up and which, after the concrete has hardened, may be employed for many purposes including the testing of the body for structural soundness.

In accordance with a more limited aspect of the invention, it is contemplated that the concrete body will be formed with a hollow core defined by a relatively rigid elongated tube surrounded by a porous fabric material. The tube may be of a plastic or metallic material and is perforated to permit the passage of water through the walls of the tube. The porous fabric is of a sufficiently close weave that water readily passes therethrough but the passage of any solid particles is restrained thereby permitting removal of excess water through the tube. After the concrete has hardened, the tube may be removed thereby leaving a hollow passage or core defined by the porous fabric in the interior of the body. This core may then be used for introducing testing equipment to verify the continuity and structural integrity of the body or the core may be used for any of a number of other purposes such as the insertion of reinforcing steel or tension rods or may simply filled in with grout.

)In accordance with another aspect of the invention, it is contemplated that an improved concrete pile or caisson may be formed by screwing a hollow shaft auger into the earths surface to the desired depth and thereafter inserting the tube or tubes enclosed in fabric into the hollow shaft of the auger. The tube smaller in outer diameter than the inner diameter of the shaft so that a clearance exists between the tube and the wall of the hollow shaft. A cementitious slurry or grout is then introduced into the clearance while, simultaneously, the auger is withdrawn creating a cavity into which the slurry flows. The tube remains in position While the auger is being withdrawn so that the slurry injected into the cavity completely surrounds the tube thereby forming a pile with the hollow core described above.

Alternatively, a concrete body may be formed in a conventional manner and, thereafter, the fabric-encased tube may be inserted into the fresh concrete to facilitate removal of the excess water as the concrete hardens or the fabric encased tube may be inserted into the open hole, casing or form prior to filling with concrete or grout.

-With either method, the tube may be used in conjunction with a vibratory source to promote the removal of water whether it may be excess water in the mix or ground water, artesian, or otherwise and to achieve a more dense concrete body.

The primary object of the invention is to provide an improved concrete body and method of constructing same.

A further object of the invention is to provide a concrete body which may readily be subjected to testing of its structural integrity.

A further object of the invention is to provide an improved method of forming concrete bodies in which a controlled tflOW path for the release of excess water is obtained and the formation of sand pockets or columns containing little or no cementitious materials in the body is minimized.

A more specific object of the invention is to provide a method of installing concrete piles in which means are provided by which the water-cement ratio of the injected grout is reduced before the concrete hardens.

To the accomplishment of the foregoing objects and advantages, as well as others, the following description, together with the attached drawings, set forth in detail a preferred embodiment of the invention. Such disclosed embodiment is not intended to be limiting since it represents but one of the various ways in which the principles of the invention may be applied.

Referring now to the drawings wherein like reference numerals indicate like parts in the various views:

FIG. 1 is a vertical sectional view of a typical prior art installation of a concrete piling.

FIG. 2 is a vertical sectional view illustrating the installation of a concrete piling in accordance with the principles of this invention.

FIG. 3 is a vertical section illustrating a concrete pile installed in accordance with the principles of the invention,

FIG. 4 is a sectional view along line 4-4 of FIG. 2.

FIG. 5 is a fragmentary perspective view of the filter sleeve and tube.

Referring now to the substance of the drawings wherein the showings are for the purpose of illustrating the preferred embodiment of the invention only, and not for the purposes of limiting same, FIG. 1 is illustrative of a typical prior art installation of a concrete pile. Thus, a cavity C is formed in the earth E, such cavity normally being formed either by an earth auger which may or may not have a hollow shaft or a hallow tubular mandrel. If the auger does not have a hollow shaft, the cavity or hole would be drilled to the proper depth and the auger would thereafter be withdrawn. After the auger is withdrawn, concrete would be introduced to the cavity C and the cavity would be filled to the proper depth whereupon the concrete would be allowed to harden to form a concrete pile P. If either a hollow shaft auger or a tubular mandrel is employed, the concrete normally will be injected as a slurry or grout through the hollow shaft or mandrel to fill the cavity formed by the withdrawal of the auger or mandrel and thereafter allowed to harden to form the concrete pile.

In either event, and as illustrated schematically in FIG. 1, piling formed by this prior art approach experience the problem of random or uncontrolled release of excess water before the grout has hardened. The occurrence is indicated in FIG. 1 by the wavy arrows which illustrate the water percolating or channeling up through the concrete in random fashion. As the water channels upward through the concrete, it carries with it fine grains of cementitious materials, leaving behind the coarser grains of sand or aggregate which tend to settle toward the bottom. The result of this segregation process is the formation of sand pockets in the concrete which destroys the homogeneous nature of the injected grout and which causes the hardened concrete pile to contain areas of varying density with widely varying bearing characteristics.

This problem of random release of Water may be compounded by the presence of water in the earth adjacent to the area in which the piling is to be constructed. Such water, which may be artesian or otherwise will also tend to flow into the cavity C and percolate upward at random points through the injected grout to form the undesirable sand pockets.

These problems in forming concrete piles are overcome by the present invention in the following manner. In accordance with conventional practice, an earth auger or drill 10 is provided, which auger has auger flights 12 extending around and along a hollow or tubular shaft 14. An appropriate tip or bit, not shown, is attached at the lower end of the auger flight and this bit preferably employs a removable or hinged plug, the construction of which is conventional in the art. Although a conventional hollow mandrel may be used in lieu of the auger, for simplicity, the invention will be described only in connection with the use of an anger.

Also in accordance with conventional practice, the auger 10 is rotated into the earths surface to the desired depth of the hole or cavity. When the proper depth has been achieved, rotation of the auger is discontinued, leaving the auger flights filled with earth. Thereupon, a hollow tube is introduced into the opening 16 of the hollow shaft 14 of the auger. It is contemplated that the tube 20 will have an outer diameter substantially less than the inner diameter of the shaft 14, so that a substantial clearance 18 will remain between the tube and the inner wall of the shaft 14. For example, the hollow shaft 14 may have an inner diameter on the order of 3 /2" while the outer diameter of the tube may be 1 /2". Obviously, other sizes of auger shafts and tubes may be employed.

The tube 20 may either be metal or plastic. With either material, the tube will include means such as perforations 22 in at least a portion of the walls thereof through which liquid may pass.

A filter sleeve 26 comprising a porous, closely woven fabric completely envelops at least the perforate portions of the tube 20. Preferably, the sleeve is composed of a nylon or other synthetic high strength fiber. Irrespective of the filter employed, it is a primary requirement of this sleeve that it be sufficiently porous to readily pass water but the pores must be sutficiently small that the solid particles of the grout are restrained from passing through the sleeve. However, the pore openings may be larger than some of the individual particles since solids will still be restrained from passing through such openings due to a bridging effect in which two or more particles attempt to pass through the opening at the same time, thus blocking the opening and thereby effectively preventing the passage of solids. A typical example of a suitable fabric is a producer bulked nylon having a 23 x 21 thread count, 965 denier, single ply plain weave. Obviously, other specific fabrics may be employed with the specified fabric merely being illustrative of a satisfactory fabric material.

Returning to the method of forming the concrete pile, the above described tube and filter sleeve are, as stated, inserted through the hollow shaft 14 with the lower end of the tube being positioned adjacent to the lower end of the hole in which the pile is to be constructed and the upper end of the tube extending above the auger. A cementitious slurry or grout is then injected in the clearance space 18 between the tube and the wall of the hollow shaft 14 with the slurry readily flowing through the hollow shaft and discharging through the removable or hinged plug at the end of the auger into the pile cavity. Simultaneous with the pumping of the cementitious slurry or grout, the auger is withdrawn from the cavity while the tube 20 is maintained in position. This is schematically illustrated in FIG. 2 wherein the lower end of the tube is illustrated as remaining in position adjacent the bottom of the pile cavity while the auger is illustrated as having been withdrawn a distance above the bottom of the cavity: The space vacated by the withdrawal of auger is filled with the cementitious grout which completely surrounds the tube as the anger is withdrawn. It will be appreciated that the presence of the filter sleeve 26 around the tube 20 prevents entry of the solid particles in the slurry into the tube through the perforations or apertures 22.

Pumping of the cementitious slurry is continued while the auger is being withdrawn until the desired level of the pile has been achieved. Thereafter, the auger is completely withdrawn from the cavity, with the resulting con struction being illustrated in FIG. 3. As is apparent from that figure, the tube 20 is positioned in the cavity and completely surrounded by the cementitious grout or slurry which now fills substantially the whole cavity.

A primary advantage of a pile constructed in accordance with the described method is schematically illustrated in FIG. 3. As shown in the figure by the wavy arrows W, the excess water present in the grout or in the adjacent soil may now travel inward to the tube 20 where it passes through the apertures 22 and upward through the core of the piling. This hollow core formed by the tube 20 provides a means for achieving a controlled release of the excess water as opposed to the random release described in connection with FIG. 1 and thereby substantially reduces the possibility that any deleterious sand pockets will be formed. Such channeling or piping as may occur in the concrete illustrated in FIG. 3 is along generally horizontal paths which are comparatively short in length and which are largely dissipated as the consolidation and settling of the grout occurs.

Another substantial advantage of the hollow core pile illustrated in FIG. 3 is that it provides a means for lowering the water-cement ratio of the grout thereby to obtain a higher ultimate strength of the hardened concrete. Thus, after the piling has been installed, a conventional submersible pump may be introduced into the tube 20 and lowered into the bottom for the purpose of removing excess water from the grout as it collects in the tube 20. Al-

tel-native to the use of a pump is the application of a vacuum at the top of the tube which will draw water from the grout into the tube 20 and upward through the tube.

A further alternative approach to effect reduction of the water-cement ratio contemplates maintaining pumping pressure on the injected grout after the cavity has been filled while restraining the grout by appropriate means from further movement upward in the cavity. The pumping pressure on the grout will cause the water in the grout to flow through the filter sleeve into the tube where it may be removed.

If the nature of the surrounding earth is such that there are faults or cracks through which the grout will fiow if subjected to pressure as described above, a further alternative approach is to employ a porous fabric bag into which the grout may be injected by the method described in copending application, Ser. No. 627,047, filed Mar. 30, 1967. The bag, together with the tube and filter sleeve, combine to provide a means for rapidly reducing the water-cement ratio across the entire cross-section of the pile. Thus, the bag is preferably of a material similar to that from whch the sleeve is formed and is capable of expressing water while retaining the solid particles of the grout. It will be appreciated that pressure applied to the grout will cause the water to be expressed inwardly through the sleeve as well as outwardly through the bag.

Still another approach is to employ the tube 2%} in combination with a vibratory source. The source may be applied to the upper end of the tube after the pile has been poured thereby to vibrate the tube from the top or, alternatively, the vibrator may be a pencil vibrator which is dropped into the tube so that the tube is vibrated from the bottom or at any point along its length. With either approach, the vibrations imported to the tube are transmitted to the concrete, thereby promoting the settling and consolidation of the concrete and enhancing the flow of Water through the perforation into the interior of the tube 20.

With each of the foregoing approaches, the net result obtained is that the excess water present in the grout is removed thereby achieving early stiffening of the grout and a higher ultimate strength of the hardened concrete. Moreover, due to the presence of the hollow core through which excess water can be removed, it is possible to employ initially a grout having a high water-cement ratio, in excess of 0.45, and thus a grout which is more readily flowable.

After the grout has begun to set, the tube 20 either may be left in position or removed. If the tube is to be removed, it is preferable that the tube be constructed from a plastic material to which the cement will bond only very slightly. The filter sleeve 26 may or may not be removed with the sleeve 29. It normally is to be expected that the tube 20, which serves only the purpose of locating the filter sleeve and supporting the sleeve until the grout has set up, will be removed While the sleeve 26, which is more intimately bonded to the concrete, will remain in the hollow core.

Upon completion of construction of the hollow core concrete pile, it may be desired simply to fill the hollow core with a grout mixture. Alternatively, the core may be used for various advantageous purposes. For example, it may be used to insert reinforcing steel or high tensile rods in the center of the pile and then introduce grout material to complete filling of the hollow core. Another use for the hollow core is to permit the insertion of a tube and packer or bag to the bottom of the pile and then pressure grout a bulb at the tip of the piling, thereby to increase the bearing characteristics of the soil adjacent to the foundation of the piling.

One substantial advantage of a hollow core is that it provides a readily available means for testing the structural integrity of the formed piling. Thus, a testing device which may operate on a wide diversity of principles such as sonic vibration or radiation may be lowered into the hollow core of the piling and used to determine the continuity and density properties of the piling. The testing device may even comprise a miniaturized television camera in the event that visual inspection is desired.

After the testing has been completed, the testing device may then be removed and the core filled with grout. As an alternative, the core may be left open and the testing equipment may periodically be lowered into the piling if the core is accessible thereby to check the integrity of the piling and its stability. As a further alternative, test equipment such as strain gauges may be permanently positioned in the core and imbedded in grout with leads from the electronic gear extending out of the core to recording equipment which can thereby keep a continuous record on the performance of the piling as stresses and strains are imposed thereon.

Irrespective of the use to which the hollow core of the piling is ultimately put, it is to be emphasized that the formation of the core as the piling is constructed is, itself, a very substantial contributing factor to the attainment of structurally sound concrete piles as described above. Thus, the benefits and advantages deriving from the presence of the core after the pile has been constructed are in addition to the basic advantage of providing a controlled release of water during the formation of the concrete piling.

The above-described approach of using a fabric encased tube to facilitate removal of excess water has applications in addition to the formation of piles and may be used to advantage in the forming of various types of concrete bodies. In addition, the tube may be installed by methods other than through the hollow shaft of an auger. For example, the fabric encased tube may simply be inserted in the fresh concrete after it has been poured rather than during the injection process or may be placed in an open hole or casing prior to placement of the concrete or grout. This approach is particularly useful in relatively short columns and may also be used in removing excess Water from poured concrete walls and like constructions. The inserted tube forms a hollow core or void in the same manner as described above and the void space may be usefully employed in the same manner.

Modifications and alterations in this invention will suggest themselves to those having ordinary skill in the art. For example, a plurality of tubes may be employed in lieu of a single tube with the tubes either enclosed in a single filter sleeve or the tubes may each be provided with individual filter sleeves. It is also contemplated that the tube or tubes may have perforations at longitudinally spaced points along the length of the tubes so that the removal of excess water may occur only at certain regions in the poured concrete. A variation of this latter approach would be to use an open ended, imperforate tube with the open end enclosed in a filter sleeve. Modifications and alterations such as these are to be included in the scope of the invention as defined by the appended claims.

Having thus described my invention, I claim: 1. A method of forming columns in the earths surface comprising the steps of forming an opening in the earths surface to the desired depth of the column by sinking a hollow shaft auger,

inserting tube means into the hollow shaft of the auger with the tube means having a diameter less than the diameter of the shaft so that a clearance exists between the tube means and the wall of the shaft,

introducing a slurry in the clearance in the shaft while withdrawing the shaft but leaving the tube means in the earth, and

continuing to withdraw the shaft while feeding slurry into the cavity vacated by the shaft until the shaft is completely withdrawn and the cavity is filled with slurry to the desired level thereby forming a column having a hollow core defined by the tube means,

said tube means including means for permittting the passage of water into the interior thereof and said method further including the step of removing water which has passed into the interior of the tube means.

2. The method of claim 1 and further including the step of introducing test means into the hollow core of the column for testing the structural integrity of the formed column.

3. The method of claim 1 wherein the slurry comprises a cementitious grout and further including the step of insetting reinforcement rods in the hollow core, and filling the core with cementitious grout.

4. The method of claim 1 wherein said step of removing water comprises the step of inserting a submersible pump into said hollow core thereby to remove the water in said core.

5. The method of claim 1, wherein the tube means includes means for permitting the passage of water into the interior thereof and said method further includes the step of extracting excess water from the slurry into the tube means.

6. The method of claim 5, wherein said extraction step comprises the application of a vacuum to the tube to draw water from slurry into the tube.

7. The method of claim 5, wherein said extraction step comprises the application of pressure to the slurry to force water from the slurry into the tube means.

'8. The method of claim 1, wherein the slurry comprises a cementitious slurry and the tube means includes means for permitting the passage of water into the interior thereof,

said slurry having a water-cement ratio in excess of 0.45

when injected through said hollow shaft,

said method further including the step of extracting a portion of the water from the slurry adjacent the tube means thereby reducing the water-cement ratio of the slurry.

9. The method of claim 1 further including the steps of inserting a second tube into the hollow core of said column, and

introducing grout under pressure through said second tube thereby to increase the bearing characteristics of the soil beneath the column.

10. The method of claim 2, wherein said testing means is positioned in said core with leads extending externally of said column, and

said core is filled with said slurry thereby imbedding said testing means in said column.

11. The method of claim 1, wherein at least a portion of said tube means is enclosed in a porous filter sleeve with said portion of said tube means including means for permitting the passage of water into the interior thereof,

said tube means and filter sleeve being inserted in a porous fabric bag means prior to being inserted into said hollow shaft,

said slurry being introduced into said bag means as said auger is withdrawn thereby inflating said bag means in the resulting cavity with said tube means and filter sleeve embedded in the slurry in the bag means.

12. The method of claim 10, wherein pumping pressure is maintained on the slurry after said bag means is inflated thereby forcing water from the slurry to pass inwardly through the sleeve into said tube and outwardly through said bag means.

13. The method of claim 12 wherein said slurry has a water-cement ratio in excess of 0.45 when injected into said bag means and said pressure is maintained until the water-cement ratio of the slurry adjacent to said sleeve and said bag means has been reduced to at least 0.35.

14. The method of claim 1 and further including the step of imparting vibrations to the tube means thereby to facilitate consolidation of the slurry.

15. The method of claim 1 and further including the step of inserting a vibratory device into said tube means and imparting vibrations to said tube means thereby to facilitate consolidation of the slurry and the flow of water into the interior of the tube means.

said bag.

References Cited UNITED STATES PATENTS Eschenbrenner 25-30 Rehmar 61-53.64 1 Moore 166-230 Smith 61-53.62 Wilhelm et al 52-310 X 2,533,263 12/1950 Johnson 264-87 X 3,464,216 9/1969 Turzillo 61-53.64

FOREIGN PATENTS 218,056 8/1958 Australia 264-86 29 8,478 1 1929 Great Britain 6 1-5 3 .62 1,003,517 1951 France 61-50 JACOB SHAPIRO, Primary Examiner 0 US. 01. X.R. 

